The Identity monad is a monad that does not embody any computational strategy.
It simply applies the bound function to its input without any modification.
Computationally, there is no reason to use the Identity monad
instead of the much simpler act of simply applying functions to their arguments.
The purpose of the Identity monad is its fundamental role in the theory
of monad transformers.
Any monad transformer applied to the Identity monad yields a non-transformer
version of that monad.